Rimmed and rimless toilet pans are known.
Rimmed toilet pans include a downward rim about the top of the pan bowl that is inwardly spaced from the inner sidewall of the bowl by a gap. During flushing, flushing water is directed along the gap in order to be distributed around the pan bowl. Some consumers dislike rimmed toilet pans as they consider the gap to be difficult to clean/disinfect.
Rimless toilet pans overcome this issue by instead using an open channel or ledge about the top of the pan bowl to direct water around and into the pan bowl. Rimless toilet pans are known with a flow splitter positioned at the rearward end of the pan bowl which splits the flushing water into leftward and rightward streams, which each then respectively travel around the leftward and rightward side of the pan. The leftward and rightward streams collide with each other at or near the frontward end of the pan. In order to concentrate the flushing energy of the colliding flushing water streams into the outlet of the pan bowl, it is desirable for the streams to meet at the front to rear centreline of the pan. However, achieving this in the practice is very difficult. If there is an imbalance in the stream and one stream travels slightly faster than the other, then their collision point can vary away from the pan centreline, causing the flushing energy to be non-optimally directed in relation to the pan outlet.